The present invention relates generally to oil field equipment and, more particularly to, to a clamp used to firmly grasp tubulars in making up and breaking down joints of the tubulars.
In handling pipe, tubing, or casing in and around a drilling rig, there are several operations which require a mechanism for firmly grasping the pipe. This has been accomplished in the past by utilizing various means ranging from devices manually wrapped around the pipe to power tongs frequently used today. The power tongs are mainly used to thread and unthread sections, or joints, of pipe when either forming or breaking down a string. In this application, two sets of power tongs are usually used. The primary set of power tongs spins a joint of pipe into or out of the string below. This setup is used both to thread joints and unthread joints, and in both operations the torque applied can be great.
Typically, the string below is retained vertically by a set of slips which wedge between the string and a bowl. These slips, however, simply provide vertical support and are not designed to counteract the torque being applied to the string by the primary power tongs. Therefore a backup set of power tongs is usually employed to hold the string fast against the torque being applied from the primary power tong.
Because of their substantial weight, power tongs are typically suspended in the drilling rig by counter weighted chains. The primary and backup tongs are sometimes hung separately and sometimes connected as a single unit. In either configuration, current power tongs are heavy and cumbersome. This is an important safety consideration. The greater the mass of machinery which is movable in an area the more likely that an injury will occur. The idea of combining the two tongs lets the worker focus on one large moving piece of machinery rather than worrying about multiple machines. However, this poses a problem in that the combined machine can weigh about twice as much as a single power tong.
Another approach to this problem is to attach the backup power tongs to the slips. The backup power tongs are thereby fixed in one location. This allows the primary power tongs to be the only hanging machinery in this operation and the focus of the worker""s attention.
Of note in either of these arrangements is that while the primary power tongs need to simultaneously grasp and spin the pipe joint being attached to the string, the backup power tongs need only grasp the string. It would be advantageous to have a power tong specially designed to only hold the pipe that is lighter and more versatile than the current backup power tong.
The backup power tongs currently in operation have another problem besides their significant weight. If a backup power tong is fixed to the slips or the platform floor and required to grasp a pipe which is fixed, the power tong and pipe are often not perfectly aligned. This misalignment can cause the backup power tong to bend the pipe or string while grasping it. It would be advantageous to have a backup power tong specially designed to be self aligning so that bending stresses are not exerted on the pipe or string.
Another application which requires a mechanism to firmly grasp the string is what is commonly referred to as a safety clamp. This is a clamp which is positioned on pipe to prevent slippage of the pipe through a set of slips. Typically, these are manually applied to a pipe. Two problems with this are that they require a worker to be in a dangerous area and the manual application does not always ensure a firm hold on the pipe. It would be advantageous to keep the worker""s hands away from such operations as much as possible and provide controlled pressure on the pipe.
The present invention is a pipe clamp for use where a lighter, remotely controlled, self-aligning mechanism for firmly grasping a pipe, tubing, casing or string is needed. This invention may be used in place of a backup set of power tongs, or alternatively as a safety clamp used in conjunction with a set of slips. The pipe clamp comprises a gripping head which wraps around the pipe, an actuator extending radially from the gripping head, and a chain wrapped around the gripping head and connected to a mount located at the radially distant end of the actuator. As the actuator expands, the chain tightens the friction surfaces of the gripping head about the pipe. The actuator floats between the gripping head and the mount giving the pipe clamp a self aligning feature. Where the actuator is hydraulic, the pipe clamp can easily be controlled from a safe, relatively remote, distance. A safety cage enclosing the mechanism is also provided which increases the safety of the device when in use.
The pipe clamp is considerably lighter than a typical set of backup power tongs. Therefore, the pipe clamp can be attached to a primary power tong without increasing the weight of the unit as much as a standard backup power tong unit would. The pipe clamp can also be attached to a slip bowl to provide a stationary backup that is safer to use than the typical power tong because of the pipe clamp""s remote operation capability. Such an application could include a set of power slips that are also remotely operated. In such an application, the only operation that the worker need worry about is the operation of the primary power tongs. A safety cage covering the power slips and pipe clamp provides added protection for the worker who remains in the area to operate the primary power tongs.
The pipe clamp can also be used as a safety clamp in conjunction with a set of slips. The pipe clamp is attached to a section of pipe extending above the slips and provides a stop in the event the pipe starts to slide through the slips. Such safety clamps are commonly manual devices. The pipe clamp of this invention allows for remote operation to keep workers out of the area as much as possible and provides a controlled grip on the pipe to ensure a firm grasp.
These and other features and advantages of the present invention will be apparent to those skilled in the art from a review of the following disclosure along with the accompanying drawings.